The large British study, begun in 1958, tracked the diet, habits and emotional and physical health of thousands of people from childhood through midlife. iStockphoto hide caption

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Gym members warm up on treadmills at Downsize Fitness in Addison, Texas. Membership at the gym is limited to people who have a high body mass index. LM Otero/AP hide caption

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Many Americans aren't getting the recommended seven to nine hours per night. Franck Camhi/iStockphoto.com hide caption

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It's not clear if diet soft drinks are the healthiest choice. ASSOCIATED PRESS hide caption

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